The percentage of those who said they did not know has fallen by six points to 19%.

The poll questioned 1,000 voters around Ireland about their intentions on Tuesday and Wednesday of this week.

FDII backs Yes vote

Food and Drink Industry Ireland, the IBEC group that represents the Irish food industry, has come out in support of the Lisbon Treaty and said that a Yes vote is the right vote for Ireland's most important indigenous sector.

FDII Director Paul Kelly said: 'As the only fully vertically-integrated industry sector in Ireland we have to deal with all aspects of the supply chain from farm to fork.

'Thus, we are exposed to a vast array of food safety and consumer protection legislation, which is mostly European in origin.

'It is clear that the sector can only benefit from a treaty that will reform how decisions are made in the EU so that Europe can remain an engine for economic growth and prosperity.

'A Yes vote is vital to protect Ireland's influence in Europe,' he said.